Inter-laboratory ring trials to evaluate serological methods for dourine diagnosis

Area of Science:

• Veterinary Immunology
• Parasitology
• Diagnostic Serology

Background:

• Dourine, caused by Trypanosoma equiperdum, is a significant equine disease.
• Accurate serological diagnosis is crucial for disease control and eradication efforts.
• Inter-laboratory reproducibility of diagnostic tests is essential for reliable disease surveillance.

Purpose of the Study:

• To evaluate the reproducibility of routine serological methods for Trypanosoma equiperdum antibody detection in equine sera.
• To assess the performance of the complement fixation test (CFT) and indirect fluorescent antibody test (IFAT) in a ring trial setting.
• To identify potential sources of variability and suggest improvements for dourine serodiagnosis.

Main Methods:

• Two inter-laboratory ring trials were conducted with 26 laboratories (22 European, 4 non-European).
• Laboratories applied the complement fixation test (CFT) and/or indirect fluorescent antibody test (IFAT).
• Sample panels included sera negative, positive, or suspected for dourine, and one serum positive for Trypanosoma evansi.

Main Results:

• The CFT demonstrated good inter-laboratory reproducibility for known Trypanosoma equiperdum positive and negative sera.
• False-positive results were observed in nine laboratories when testing a Trypanosoma evansi-positive serum using CFT or IFAT.
• Seropositivity was confirmed in one of three horses initially suspected of dourine.

Conclusions:

• The CFT is a reliable method for dourine serodiagnosis, but its specificity can be compromised by cross-reactivity with Trypanosoma evansi.
• Standardizing critical reagents, such as antigens and developing a standard Trypanosoma equiperdum serum, could improve diagnostic specificity.
• Implementing a standardized low-titer serum control is recommended to ensure consistent test sensitivity across laboratories.